1. Technical Field
The present invention relates to a test apparatus.
2. Related Art
When testing a device under test such as a semiconductor circuit, a power supply apparatus that supplies current to the device under test is unable to quickly track fluctuation in the current consumed by the device under test. Japanese Patent Application Publication No. 2001-195139 discloses providing a bypass capacitor to the power supply line near the device under test to solve this problem.
When there is great fluctuation in the power supply current, a bypass capacitor conductor with a high capacitance, e.g. tens of μF, is provided to track this fluctuation. A small output current of the power supply apparatus is measured to measure a small current such as the standby current. In this case, the load capacitance connected to the power supply apparatus is limited, and so a reed relay is provided to separate the high-capacitance capacitor from the power supply line.
However, there is a limited space near the device under test, and so the reed relay cannot be provided. Therefore, the high-capacitance bypass capacitor is provided at a position that is not near the device under test.
As a result, the power supply line is lengthened from the bypass capacitor to the device under test, which increases the inductance component between the bypass capacitor and the device under test. Therefore, it is difficult to supply a high-frequency current from the bypass capacitor to the device under test.
One test that can be performed on the device under test is a test for measuring the current consumed when the device under test is operating. In this test, the current consumed by the device under test is measured by measuring the current flowing through the power supply line. More specifically, the current consumed by the device under test is measured by measuring the current flowing through the power supply line at a position closer to the device under test than to the bypass capacitor.
However, as explained above, it is difficult to supply a high-frequency signal from the high-capacitance bypass capacitor to the device under test. Therefore, even if the current flowing thought the power supply line is measured between the high-capacitance bypass capacitor and the device under test, it is difficult to accurately measure a current consumed by the device under test that fluctuates at a high frequency.